Metamaterial Array Research Articles

An Exhaustive Analysis of the Characterization of Photopolymer Material (SZ2080) by Two-Photon Polymerization, Waves Moving in a Periodic Potential, and Two-Photon Absorption

This paper presents an Exhaustive Analysis of the Characterization of Photopolymer Material (SZ2080) by Two-Photon Polymerization, and some of the modern concepts like Characterization of Photonic Crystals in Photopolymer SZ2080 by Two-Photon Polymerization, Waves Moving in a Periodic Potential, and Optical Quantum metamaterials. Two-photon polymerization for fabricating three-dimensional subdiffraction-limited structures has been discussed. Experimental and Computed Curves of line thickness (nm) vs feed rate (μm/s) have been technically analyzed. Waves moving in a Periodic Potential and Photonic Crystals have been technically discussed. In addition, Optical Quantum metamaterials have been discussed in terms of quantum coherence, and quantum dots with emphasis on cavity array metamaterial.

Mimicking bio-mechanical principles in photonic metamaterials for giant broadband nonlinearity

Microscopic structuring can change the effective properties of a material by several orders of magnitude. An example of this is animal bone, which has an effective elastic modulus that is more than 1,000 times larger than that of the constituent proteins. Here, we propose a broadband-enhancement principle of photonic nonlinearity that has a similar mathematical origin as the bone example. The proposed staggered array metamaterials violate the standard Miller’s rule in nonlinear optics and can enhance the third-order nonlinearity by more than a thousand to a billion times, depending on target operation frequencies. This metamaterial principle also enables manipulation of the individual components of the linear and nonlinear susceptibility tensors. Our biomimetic approach overcomes the fundamental speed-efficiency trade-off in current resonant enhancement schemes, making faster and more efficient all-optical devices possible for 1.55 μm wavelength. The principle is also applicable to ionic diffusion, heat conduction, or other transport problems.

Simulation and fabrication of a single-band tunable absorber in 20–50 THz range based on cross array metamaterials

In this paper, a tunable metamaterial is designed and measured in the 20–50 THz band. An absorption peak (80%) is obtained at resonance frequency point 40THz based on the LSP mode resonance on the surface of metal array and the dielectric loss mode in two dielectric layers. In experiments, the amplitude is increased and the resonance frequency is reduced through decreasing the lattice constant P or increasing the side length W1. In the third and fourth sets of experiments, this absorption peak can be controlled through increasing or reducing the temperature. This is due to the insulator-metal or metal-insulator phase transitions are achieved. Moreover, under the room temperature 300 K and normal pressure, the absorption amplitudes are enhanced and the resonance frequency is shifted with different liquid layers. This sample shows the feasibility of application to temperature or liquid sensing.

Multi‐functional sandwich structure with metamaterial antenna lattice cores: protection, radiation and absorption

In this study, a multi-functional sandwich structure is proposed with mechanical support, electromagnetic radiation and absorption by radome-integrated design of metamaterial antenna array. The pyramid metamaterial absorber (PMA) is used as the radiator of the antenna element, with a fibre-reinforced resin composite radome attached on the top. To enhance mechanical strength of the radome and meanwhile to reduce radar cross-section (RCS) of the antenna, the PMA is used as the lattice core of sandwich structure. By engineering the dispersion, the PMA structure is used as low-loss antenna in-band radiator and broadband out-of-band absorber simultaneously. For instance, an antenna working in the C-band and with RCS reduction in the X-band was designed, manufactured and measured. Radiation performances of the antenna are verified. A 5 × 5 antenna array and a 2 × 2 array were also fabricated to evaluate the absorption and mechanical properties, respectively. Measured results of the 5 × 5 array present that the RCS reduction is more than 20 dB in the X-band. Quasi-static out-of-plane compression tests on the 2 × 2 antenna array verify the good mechanical performances. The sandwich structure can achieve high mechanical strength, good radiation performance and low RCS, which provides a new paradigm of antenna–radome-integrated design for practical applications.

A tunable terahertz metamaterial absorber composed of elliptical ring graphene arrays with refractive index sensing application

In this paper, we demonstrate a tunable absorber composed of periodically patterned elliptical ring graphene metamaterial arrays. An absorption peak at 53.6μm with the maximum absorption of 49.2% of pure graphene layer has been realized. The effects of different parameters are studied by the Finite Difference Time Domain (FDTD) method. Besides, we simulate the spectra as the surrounding refractive index changes to better evaluate the sensing performance of the structure, producing a structure with the sensitivity up to 14110 nm/RIU. Finally, this paper also analyzes the absorption characteristics of bilayer graphene structure, and has a tunable dual-band selective absorption effect with a maximum absorption of 49.6%. Based on the research, it is more convenient to design the graphene-based optoelectronic devices, biosensor and environmental monitor.

Theory, Design, and Implementation of a New Family of Ultra-Wideband Metamaterial Microstrip Array Antennas Based on Fractal and Fibonacci Geometric Patterns

The theory and design of a new family of ultra-wideband (UWB) metamaterial (MTM) microstrip array antennas based on fractal and Fibonacci geometric patterns are investigated. First, the UWB microstrip array antenna is presented with two radiating MTM elements. Then, using fractal and Fibonacci geometric patterns, the array antenna is expanded. Improvements in the antenna parameters is achieved by repeating the second and third iterations of the fractal and Fibonacci patterns. As the order of iteration of the fractal and Fibonacci geometric patterns increases, the impedance bandwidth of the MTM microstrip array antenna increases, and its radar cross-section (RCS) decreases. The impedance bandwidth of the array antenna with two MTM elements is 3.37–9.2 GHz, while the bandwidth of the third-iteration Fibonacci and fractal MTM array antennas are 3.5–10.1 GHz and 3.55–10.34 GHz, respectively. Furthermore, the proposed array antennas exhibit lower RCS due to metal area reduction, with respect to the array antenna with two MTM elements.

Lattice‐Enhanced Fano Resonances from Bound States in the Continuum Metasurfaces

AbstractFano resonances in metamaterials are known for their high quality (Q) factor and high sensitivity to external perturbations, which makes them attractive for sensors, lasers, and nonlinear and slow light devices. However, Fano resonances with higher Q factors obtained through structural optimization of individual resonators are accompanied by lower resonance intensity, thereby limiting the overall figure of merit (FoM) of the resonance. Here, a strategy for simultaneously enhancing the Q factor and FoM of Fano resonances in terahertz metamaterials is reported. Coupling of the Fano resonance, which arises from a symmetry‐protected bound state in continuum, to the first‐order lattice mode of the metamaterial array leads to stronger field confinement and substantial enhancement of both Q factor and FoM. As such enhancement occurs in planar metamaterials independently of the resonator geometry, the proposed approach can be utilized for a wide range of high‐Q and high‐sensitivity terahertz metadevices.

Metamaterial Loaded Nine High Gain Vivaldi Antennas Array for Microwave Breast Imaging Application

In this article, a metamaterial loaded high gain nine antennas based microwave breast imaging system has presented to detect an unwanted tumour in the breast phantom. The proposed antenna is designed on a modified version of a basic Vivaldi antenna. Single negative metamaterial structure has been loaded to the modified version Vivaldi to enhance far-field antenna properties like gain and radiation pattern, which is essential for the breast imaging system. The proposed antennas have achieved −10dB impedance bandwidth of 8.45 GHz (2.0- 10.45 GHz) and 7.9 dBi maximum gain in the operating band. To verify the time-domain performance, the fidelity factor is also calculated for the face-to-face orientation, which is near about 92.89%. After optimisation in high load phantom, near field directivity (NFD) is also analysed with the workload to ensure that the near field radiation properties. Finally, the nine metamaterial (MTM) antennas arrays are placed around the breast phantom in a hemispherical order to take the data of scattering parameters for tumour object analysis in a CST simulation environment. The extracted data has been processed through an imaging algorithm to reconstruct the image for identifying the unwanted tumour object inside the breast phantom.

A Survey of Performance Enhancement Techniques of Antipodal Vivaldi Antenna

The increasing proliferation of advanced devices for UWB, 5G communication, micrometer-wave, and millimeter-wave communication demands an antenna which can handle huge data rates, provides high gain and stable radiation pattern as a panacea of most of the current wireless communication problems. Many different antenna designs have been proposed by the researchers but, Antipodal Vivaldi Antenna (AVA) has drawn the attention of most of the researchers because of its high gain, wide bandwidth, less radiation loss, and stable radiation pattern. Different methods are presented to make AVA more compact while maintaining the performance of an antenna to an acceptable level. These different methods are substrate choice, flare shape, slots, and feeding connectors. Also, AVA performance can be enhanced by incorporating corrugation, dielectric lens, patch in between two flares of AVA, balanced AVA (BAVA), metamaterial, computational intelligence (CI), and AVA array. The AVA performance enhancement techniques modify the electrical and physical properties of an antenna which in turn improves its performance. A large number of performance enhancement methods of AVA design have been proposed, however, no comprehensive study exists to categorize these performance enhancement techniques and outline their concepts, advantages, disadvantages, and applications. So, in this paper, we have attempted to outline all methods available for enhancing and optimizing the parameters of AVA. Additionally, to validate some of the important performance enhancement methods, they are incorporated in the basic conventional AVA design and further simulation results are obtained for the same which are in line with the surveyed literature. Each method is explained in detail by incorporating its key points, merits, and demerits. Moreover, illustrations from the literature are given to demonstrate improvement in the parameters as a result of applying a particular performance enhancement technique.

Lattice Collective Interaction Engineered Optical Activity in Metamaterials

AbstractThe metamaterials with chiral metamolecular structure designs would show optical activity. In the past, researchers devoted themselves to proper designs of the individual metamolecules to improve the optical activity performance, however the roles of the lattice collective modes in the metamaterial array to the final optical activity have received much less attention. Here, how collective resonances can be utilized to engineer the optical activity of the metamaterials is systematically studied. Metamaterial arrays consisting of various numbers of “L”‐shaped chiral metamolecules are fabricated. It is illustrated that the intermolecule collective interactions are capable to dramatically improve the quality factor of the resonances of metamolecule ensembles. Also, it is shown that with the aid of lattice collective resonances, the spectral linewidth of the optical rotation and ellipticity angle modification to the light collapse efficiently and the magnitudes of the optical activity effects can be dramatically boosted. Both the spectral line collapses and the optical activity magnitude becomes saturated as the size of metamaterial array becomes larger than certain sizes, which implies the maximum coupling length between the metamolecules. The results provide a new freedom in optimizing the optical activity of the chiral metamaterials.

Bandwidth enhancement of five-port reflectometer-based ENG DSRR metamaterial for microwave imaging application

A five-Port Reflectometer (FPR) with the integration of ultra-wideband (UWB) Epsilon Negative (ENG) Double Split Ring Resonator (DSRR) metamaterial array is introduced in this paper for microwave imaging (MWI) application. The designed DSRR consists of two concentric rings with a split in each which are spatially rotated by 180°, formed an inverted structure to exhibit a wide negative epsilon bandwidth of 187 % (from 0.5 GHz to 15 GHz). The FPR is designed using a ring junction topology and semi-circularly curved inter-port transmission lines (TLs) which are placed between five equally spaced ports. Localizing the DSRR metamaterial in a periodic array of 5 × 4 at the ground plane of FPR lead to 79.79 % fractional bandwidth and reflection coefficient within the operating frequencies of 0.991 GHz–2.2576 GHz. Equivalent circuit model has been alluded with an intricate description of different array configurations of the metamaterial unit cell. Comparison of EM simulation and circuit simulation has been performed to validate the equivalent circuit model. It is found that the existence of stray capacitance, Cstray which is represented by the DSRR configurations, significantly influenced the resonant frequency and bandwidth of FPR. Measured results of the proposed design suits well with the simulations and prove higher efficacious applicability of the proposed design for microwave imaging application. A comparison of the reconstructed image also proves its suitability for the microwave imaging application.

Improving airborne far-field ultrasound acoustic imaging systems using high-K acoustic metamaterial

Airborne far-field ultrasound acoustic imaging systems allow scanning a large area that light-based imaging systems fail, such as glass walls and smoky environments. To scan the environment with great details, High-frequency acoustic waves should be used, but high-frequency waves attenuate fast, and it leads to low-range imaging. To address this challenge, a high-k acoustic metamaterial is used. This metamaterial is constructed of a subwavelength sequence of air-material layers and compresses the wave in a way that sound pressure increase in a particular frequency. In this research, a Uniform Linear Array consists of 30 microphones that designed to get a real-time 2-D image of the environment. Using this metamaterial increases the imaging range from 6 m to 15 m. It also improves the capability of the system to recognize small obstacles. By using the metamaterial array, an obstacle with a diameter of 1 cm is visible at a distance of 6 m while the smallest recognizable obstacle for the microphone array at the same distance has the diameter of 6 cm. The effect of the obstacle size and distance on image amplitude has been investigated and compensated. It is concluded that using metamaterials do not only increase the signal to noise ratio but also increase the quality of the image of a complex environment which consists of obstacles with different diameters.Airborne far-field ultrasound acoustic imaging systems allow scanning a large area that light-based imaging systems fail, such as glass walls and smoky environments. To scan the environment with great details, High-frequency acoustic waves should be used, but high-frequency waves attenuate fast, and it leads to low-range imaging. To address this challenge, a high-k acoustic metamaterial is used. This metamaterial is constructed of a subwavelength sequence of air-material layers and compresses the wave in a way that sound pressure increase in a particular frequency. In this research, a Uniform Linear Array consists of 30 microphones that designed to get a real-time 2-D image of the environment. Using this metamaterial increases the imaging range from 6 m to 15 m. It also improves the capability of the system to recognize small obstacles. By using the metamaterial array, an obstacle with a diameter of 1 cm is visible at a distance of 6 m while the smallest recognizable obstacle for the microphone array at t...

Utilizing a spark gap generator as an impulsive noise source for scale model experiments investigating novel metamaterial arrays

Utilizing a spark gap generator as an impulsive noise source for scale model experiments investigating novel metamaterial arrays

Graphene-Integrated Metamaterial Device for All-Electrical Polarization Control of Terahertz Quantum Cascade Lasers

Optoelectronic modulators that operate by the electrical tuning of plasmonic resonator structures have demonstrated fast (>MHz) manipulation of terahertz (THz) radiation for communications, imaging, and spectroscopy applications. Among this class of THz device, chiral metamaterial-based polarization modulators have attracted increasing attention due to the importance of THz polarization control for chemistry, biology, and spectroscopy applications, as well as for THz communication protocols. In this paper, active polarization modulation of a THz quantum cascade laser is demonstrated by the electrical tuning of a 2D chiral metamaterial array. The operating principle of this device is based on an electromagnetically induced transparency analogue, produced by the coupling between a bright resonator and two dark resonators. The orientation of these resonators is such that a radiating electric dipole orthogonal to the incident electric field polarization is induced, causing a rotation of the polarization angle of the transmitted radiation. By variably dampening the dark resonators using graphene, the coupling condition is electrically modulated such that continuous tuning of the transmitted polarization angle is achieved. This device, operating at room temperature, can be readily implemented as a fast, optoelectronic, polarization modulator with a maximum tuning range of 20 degrees at 1.75 THz, with demonstrated reconfiguration speeds of >5 MHz.

Reflected wave manipulation via acoustic metamaterials with decoupled amplitude and phase

We present the analytical derivation and numerical simulation for the wavefront manipulation of reflected waves at a lossy surface. It is found that the incident plane wave can be reflected in the desired direction or conversed to the trapped surface mode without parasitic scatterings by introducing acoustic energy loss at the surface. To realize the lossy inhomogeneous surface, holey-structured acoustic metamaterial arrays with decoupled reflection amplitude and phase are used. Anomalous reflection phenomena, including non-specular reflection, negative reflection, and conversion of the propagating wave into the surface wave, are achieved by modulating the decoupled amplitude and phase. Our results provide a practical and straightforward way to manipulate the reflected waves, which can also be extended to the three-dimensional wave propagation.

Annular antenna array metamaterial with SINIS bolometers

We fabricated and experimentally studied a wideband metamaterial comprising a 2D array of annular antennas with Superconductor-Insulator-Normal metal-Insulator-Superconductor (SINIS) bolometers. The annular antenna array metamaterial was designed for a frequency range of 300–450 GHz and consists of periodically arranged electrically small rings, each containing two or four SINIS bolometers connected in series or parallel. These periodic structures with a unit cell size of about one-tenth of a wavelength act as a distributed absorber and receive two orthogonal polarizations. The unit’s small cell size provides a higher density of bolometers and therefore increases the bandwidth and the dynamic range of a single pixel. Theoretical estimates at a central frequency of 345 GHz yield absorption efficiencies of over 80% of the incident RF power within the 300–450 GHz frequency range. The average absorption by the metamaterial matrix in the given frequency band is at least twice as high in comparison to the half-wave circle matrix. We measured the optical response at sample temperatures as low as 100 mK using a quasi-optical setup that consisted of an immersion sapphire lens, bandpass mesh filters, and a variable temperature cryogenic blackbody radiation source. The measured series array voltage responsivity was 1.3 × 109 V/W for radiation temperatures ranging from 2 K to 7.5 K. The current responsivity for the parallel array was 2.4 × 104 A/W at a bath temperature of 100 mK. The spectral response was measured in a 240–370 GHz range with a Backward Wave Oscillator radiation source. The measured equivalent temperature sensitivity could be reduced to 100 μK/Hz1/2 at a 2.7 K radiation temperature level, a value that is suitable for anisotropy measurements in cosmic microwave background radiation.

Near-zero metamaterial inspired UHF antenna for nanosatellite communication system

Epsilon-and-mu-near-zero (EMNZ) metamaterial structure inspired UHF antenna for nanosatellite has been proposed in this paper. The antenna consists of 3 × 2-unit cell array on the ground plane and a meander line radiating patch. Coaxial probe feeding technique has been obtained to excite the antenna. The meander line enables the antenna to resonate at lower UHF band and the metamaterial array is used to make the resonant frequency stable by reducing the coupling effect with metallic nanosatellite structure. The metamaterial structure exhibits EMNZ characteristics from 385 MHz to 488.5 MHz, which facilitates stable resonant frequency and higher antenna efficiency when embedded with nanosatellite structure. The proposed EMNZ inspired antenna has achieved measured impedance bandwidth (S11 < −10 dB) of 14.92 MHz (391 MHz–405.92 MHz). The perceptible novelty of this paper is the development of EMNZ metamaterial that significantly improves the UHF antenna’s operating frequency stability as well as efficiency for low earth orbit nanosatellite communications.

Design and measure of a tunable reflection polarization converter based on hybrid dielectric layer metamaterials

We design and experimentally investigate of a temperature sensitive reflection polarization converter based on circular hole array metamaterial. This achieved converter consists of two metal layers (silver) and three dielectric layers (SU-8, polyimide, VO2). Measured results reveal that two polarization conversion ratio (PCR) peaks are obtained (99.1%, 99.3%) at two neighboring frequencies at normal temperature, which are derived from the cavity and electrical resonance modes, respectively. A PCR band is achieved based on the overlap of two PCR peaks, and the average conversion rate reaches 94.2%. When the measured temperature is increased, the average value of the PCR band is enhanced. Moreover, a new PCR peak is achieved with the measured temperature increasing, which is derived from a new electrical resonance mode excited between the bottom metal layer and the VO2 layer.

Terahertz Microfluidic Metamaterial Biosensor for Sensitive Detection of Small-Volume Liquid Samples

Metamaterial (MM) assisted terahertz (THz) label-free biosensing has promising applications. However, the sensitive THz detection of highly absorptive liquid samples remains challenging. Here, we present a novel multi-microfluidic-channel MM biosensor for highly sensitive THz sensing of small-volume liquid samples. The multichannels are set mostly in the strong electric field enhancement area of the MM, which significantly decreases the liquid's amount and enhances the interaction between the sensing targets and the THz wave (thus increasing the sensitivity). The sensing results of isopropyl-alcohol–water mixtures and bovine serum albumin solutions based on the bow-tie array MM with multichannels demonstrate the effectiveness of the proposed design and the great potential in THz biosensing. This design has the advantages of being highly sensitive, label-free, cost-effective, easy to operate, and only needing a tiny liquid volume. Thus, our device provides a robust route for MM-assisted THz label-free biosensing of liquid-based substances.

A Symmetrical Dual-Beam Bowtie Antenna With Gain Enhancement Using Metamaterial for 5G MIMO Applications

A symmetrical dual-beam end-fire bowtie antenna with gain enhancement is achieved by integrating three pairs of metamaterial (MTM) arrays for 5G MIMO applications. The first pair of MTM array with high refractive index (HRI) are deployed to form a wide beam antenna. The second pair of HRI MTM array are arranged along the end-fire direction (x-direction) in front of the radiators in order to split the single wide beam into dual beam. Besides, the third pair of anisotropic MTM array with HRI along x-direction and near zero refractive along y-direction are incorporated in front of the second pair of MTM array to improve the gain performance. The proposed technique is verified by both the full-wave electromagnetic simulation and experiment, and the simulated and measured results agree very well with each other. Moreover, the measured results reveal that the main beam directions of the proposed antenna point to ±30° with respect to the end-fire direction (0°) over 24.25-27.5 GHz, with a maximum gain of 7.4 dBi at 26 GHz and a 4.2 dB gain improvement compared to the wide beam antenna.